Leonardo da Vinci is credited with designing an early hygrometer, an instrument for measuring humidity.
His design used the change in weight of an absorbent material to indicate moisture in the air. A dry substance and a moisture-absorbing substance could be compared or balanced, allowing atmospheric dampness to be estimated. The instrument reflects Leonardo's interest in turning natural observations into measurable quantities.
A hygrometer measures humidity, while an anemometer measures wind speed. The two instruments are sometimes confused because Leonardo studied both air movement and atmospheric conditions in connection with flight.
Later hygrometers used hair, mechanical elements, or chemical materials, and modern devices commonly use electronic sensors. Leonardo's proposal was an early scientific instrument concept, not the direct ancestor of every modern humidity sensor.